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How to Calculate Weather-Normalized Energy Consumption

Updated: Oct 29, 2023


weather normalization ,  weather data for energy usage

Weather Normalization: Optimizing Energy Consumption Across Climates

If you are an asset manager with properties in regions with different weather conditions or If you are a company with branches distributed over the whole country or different continents, such as hotels, gas stations, and supermarket chains; You may need to review the energy consumption of your properties and have a reliable and fair metric to compare your branches to establish energy efficiency strategies and avoid revenue losses in your business. In this blog post, we explain to you how we calculate weather normalization via a standard method. This method will be also useful for managers who handle one commercial building and want to normalize their consumption over various seasons (Especially hotel managers).

weather normalization 
, weather data for energy usage

Heating and Cooling Degree Days

Heating and Cooling Degree Days (HDD and CDD) is a unit of measurement that has been adopted by the ASHRAE organization as the industry standard for weather normalization models. HDD and CDD indicate how hot or cold is outside for a given day and for how long it was at that temperature. This can be more helpful than knowing the temperature alone for estimating how much energy you use on heating and air conditioning. National Grid notes that studying degree-day patterns can help energy managers evaluate the oscillating trends in energy bills.

In order to calculate the HDD and CDD, you need to define your base temperature (the temperature at which your building needs no heating and cooling). For example, 20 degrees in a city like Lisbon is the base temperature for most of the buildings (but it varies building by building related to natural sun lights and ventilation, age, and construction material of the building). Then obtain the average outdoor temperature for a day (which is available online). If the average outdoor temperature is exactly equal to the base temperature (20 degrees), the HDD and CDD are zero. If it is above the base temperature, subtract it from the base temperature to find the CDD and If it is below the base temperature, subtract it from the base temperature to find the HDD. For example, if the high temperature of a day in Lisbon is 28 degrees and the low temperature is 18 degrees, the average temperature is 23 degrees. Subtracting 23 from 20 equals 3, which indicates that there were 3 CDD for this day. To normalize the electricity consumption of buildings based on HDD and CDD, the following steps should be taken:

  1. Sum the total heating and cooling degree days for one building for any required period.

  2. Divide the total kWh consumed in the same period by the total number of heating and cooling degree day.

Conclusion

Weather normalization is a pivotal concept for businesses and asset managers with properties in diverse climatic regions. It offers a reliable metric to assess energy consumption across different locations, ensuring a fair comparison and aiding in the formulation of energy efficiency strategies. This process primarily revolves around the calculation of Heating and Cooling Degree Days (HDD and CDD), which serve as indicators of external temperature variations and their duration. By establishing a base temperature and analyzing daily average outdoor temperatures, one can determine HDD and CDD values. These values, in turn, facilitate the normalization of electricity consumption across buildings, providing a clearer perspective on energy management tailored to weather variations. Whether overseeing a single commercial establishment or a chain of hotels, gas stations, or supermarkets, understanding weather-normalized energy consumption is indispensable for optimizing energy use and preventing potential revenue losses.



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